@alex-74 You’re right, that’s not a good thing. At this time, cannot do a simple check to see what’s wrong with your install as registration is required. Do provide us with a throw-away regular member login username and password which you can later delete after issue is resolved.

What have you tried so far to troubleshoot this issue? Changing to BP Default theme to check if issue is corrected? Deactivating other BuddyPress plugins to check for plugin conflicts? If you want to deactivate plugins by batches, I would deactivate the chat plugin and those plugins which have not been updated for BP 1.6-1.7, then check if you could go to a group’s single page. If it’s still not working, deactivate another batch of plugins.